This invention relates to a string-like silicon carbide heating element circular or rectangular in cross section, more particularly, to a method of producing a string-like silicon carbide heating element circular or rectangular in cross section, which is suitable for use as an ignition means of a combustor which burns natural gas, petroleum, etc.
Resistance heating elements widely used nowadays include a nonmetallic element and a metallic element like a heating wire. A string-like heating element is widely known to the public when it comes to a metallic heating element such as nichrome or kanthal alloy. But, a string-like heating element has not yet been developed when it comes to a nonmetallic heating element such as silicon carbide.
The conventional method of producing a silicon-carbide heating element comprises the steps of adding an inorganic binder to a powdered .alpha.-silicon carbide, shaping the mixture into a rod or a hollow cylinder, and sintering the shaped body at temperature higher than 2,000.degree. C. Naturally, the resultant heating element is formed mainly of .alpha.-silicon carbide. Such a conventional silicon carbide heating element in the form of a rod or hollow cylinder is about 6 mm or more in diameter. As a matter of fact, a heating element of this type having a diameter smaller than about 6 mm is unknown to the public. The large diameter mentioned leads to a low resistance of the heating element, through the conventional silicon carbide heating element has a resistivity of about 0.03 to 0.15 .OMEGA..multidot.cm, resulting in that it is impossible to connect the heating element directly to a household power source of 100 V or to a 12 V cell. Under the circumstances, it is customary to use a metallic heating element for forming an ignition means of a small room heater utilizing the combustion of natural gas, petroleum, etc. On the other hand, the use of the conventional silicon carbide heating element is restricted to a field such as industrial electric furnace.